(photo by Detroit Golfer)
They don’t. The idea that professional boxers, or any other martial artists/combat athletes for that matter, are required to “register their hands as lethal weapons”, is a complete myth.
It’s a silly boast that some fighters use to exaggerate their own ability.
This is a myth begun by the Joe Louis team, who had actors dressed as policemen arriving to “register” The Brown Bomber’s hands before many of his fights.
After Joe Louis started doing it as a stunt, the myth was likely perpetuated by trainers offering this registration as a service.
What is true is that if a trained boxer assaults someone, or gets into a fight and kills/maims someone with their punches, then a court of law may view this as aggravated assault.
Skilled fighters understand that there is a strong chance that they will cause serious harm in a fight, so they have a greater than normal duty of care to avoid physical conflict and to warn others of the danger they pose in any altercation.
There is another common myth that fighters are legally obliged to warn an attacker three times that they are a pro boxer before retaliating, but this is also untrue.
Three warnings is a reasonable guideline but obviously, if the assailant is an immediate physical threat, the boxer has the same right to self defense as anyone else.
Courts would look at each instance on a case-by-case basis and decide whether the boxer (or otherwise highly trained fighter) took reasonable steps to avoid a fight, but this is always pretty subjective.
In short – don’t believe everything your hear from some guy in a bar. It’s usually nonsense.